}

  public void testCeilingEntry() {
    create().ceilingEntry("a");
  }

  public void testCeilingKey() {
    create().ceilingKey("a");
  }

  public void testDescendingKeySet() {
    NavigableMap<String, Integer> map = create();
    NavigableSet<String> descendingKeySet = map.descendingKeySet();
    assertTrue(descendingKeySet instanceof SynchronizedNavigableSet);